The widespread interest in ball sports, particularly baseball and tennis, has stimulated numerous proposals for power-driven ball throwing equipment enabling athletes to develop playing skill without need for opponents. Prior proposals to meet this need are subject to many disadvantages and shortcomings including complexity, excessive weight, high cost, unsuitability for transport except by truck, requiring handling by two or more persons and an available source of power. A major source of the size and weight of prior machines is the motor components having the requisite speed and torque characteristics to throw balls as often as once each second while maintaining a constant ball throwing velocity. Prior machines have achieved constant ball throwing velocity by using such large and powerful motors that their speed drops negligibly and recovers almost instantaneously while throwing a ball. The power requirements for motors meeting these needs have been grossly in excess of that available by storage batteries of a reasonable size for on-board portable use. No such equipment or machine to date has been perfected or is available which overcomes these disadvantages and shortcomings.